Leslie Moonves and Philippe Dauman were among the guests at Vibrato in Bel Air for a soiree in honor of the Viacom and CBS mogul's "passion to party."

A humble strip mall in tony Bel Air was abuzz on Wednesday evening as guests began to trickle in for Sumner Redstone's 92nd birthday party.

Redstone, the frail media mogul whose National Amusements controls CBS and Viacom, was the guest of honor at an intimate birthday affair thrown by current girlfriend Sydney Holland and ex-flame Manuela Herzer at the shopping center's understated Vibrato jazz club and restaurant. The guest list for the event, whose invitation promised a celebration of Redstone's "passion to party," included singer Tony Bennett, who, according to guests who attended, serenaded Redstone with a series of songs including "I Left My Heart In San Francisco." Also in attendance: CBS chief Leslie Moonves, Viacom CEO Philippe Dauman, Paramount chairman Brad Grey and COO Tom Dooley,financier and philanthropist Michael Milken,investor Ron Burkle, formerParamount execs Jonathan Dolgen and Sherry Lansing (with her husband, director William Friedkin), philanthropist Barbara Davis, producer Mike Medavoy and wife Irena, Redstone and Holland attorney Patty Glaser and producers Lawrence Bender and Robert Evans.

Notably not in attendance (nor invited to the party) were Redstone's children, Shari or Brent Redstone. Their relationship with their father — as well as his deteriorating health — has been under scrutiny in recent months as he has failed to appear at CBS and Viacom events even though he remains in control of the two publicly traded media companies.

Redstone, who has withdrawn considerably from public view since his last in-person interview with The Hollywood Reporter in 2014, entered the Bel Air birthday bash via a side entrance with the help of several aides. A portable black curtain was erected at the Vibrato entrance to shield him from public view as a herd of security guards patrolled the area in front of the small jazz club and restaurant to ensure privacy.

Inside, Holland, 43, andHerzer, 50, both dressed in elegant evening gowns, sat at a booth with Redstone as well-wishers approached with birthday greetings. Attendees say the party was crowded and the mood was festive. Redstone was presented with an enormous cake decorated with frosting fish (he is a fan of aquariums) but did not make a speech.

But a rager it was not: The event, which began at 6 p.m., wrapped in fewer than two hours and Redstone — walking out of the venue with a fair bit of assistance — left through the side entrance before 8 p.m. Bodyguards had re-erected another portable curtain (they had to fend off at least one videographer).

According to sources, the mogul's 92nd birthday was originally supposed to be a larger affair on the Paramount lot, but concerns about his health — and surrounding him with a large crowd — led to the more modest alternative in Bel Air, a stone's throw from Redstone's Beverly Park home.

Outside, as the crowd left the venue almost immediately after Redstone did, the constellation of Maseratis, Ferraris and Maybachs was replaced by the strip mall's usual collection of more modest cars.